Background: Cyclops syndrome is a common yet poorly understood complication after anterior cruciate ligament (ACL) reconstruction (ACLR), resulting in loss of knee extension that sometimes requires revision surgery for debridement. Limited agreement in the literature exists on the risk profile of patients who develop cyclops syndrome. Purpose/Hypothesis: The purpose was to define a risk profile indicating which individuals are predisposed to reoperation for cyclops syndrome after primary ACLR. It was hypothesized that high posterior tibial slope (PTS), narrow notch, large grafts, and higher grades of remnant preservation would be associated with reoperation for cyclops syndrome. Study Design: Case-control study; Level of evidence, 4. Methods: Primary ACLRs performed by academic sports medicine surgeons at a single large integrated health care network between 2014 and 2021 were included. Variables including patient characteristics, knee hyperextension, instability grade, graft type and diameter, meniscal procedures, femoral notch width, ACL remnant preservation, graft/tissue impingement, tunnel position, and PTS were collected. Univariate analyses and multiple regression were performed to identify risk factors associated with reoperation for cyclops syndrome within 24 months after ACLR. Results: A total of 1163 consecutive primary ACLRs were included (mean age, 24.9 years). The overall rate of reoperation for cyclops syndrome was 5.5%. No statistically significant differences in rates of reoperation for cyclops syndrome were identified based on surgical timing, graft type, graft diameter, or meniscal repair. Additionally, ACL remnant grade, excessive graft anterior tissue coverage, and tibial tunnel position were not associated with the development of symptomatic cyclops syndrome. On univariate analyses, contralateral knee hyperextension ( P = .04) and increased PTS >12° ( P = .004) were found to be potential risk factors for cyclops syndrome. After controlling for PTS, narrow femoral notch, and femoral tunnel placement, stepwise subset multiple regression analysis (n = 351) identified knee hyperextension as an independent predictor of reoperation for cyclops syndrome (OR, 2.40; P = .049). Conclusion: After controlling PTS, narrow femoral notch, and proximal femoral tunnel placement, contralateral knee hyperextension was found to be an independent predictor for reoperation for cyclops syndrome necessitating surgical debridement after primary ACLR. Surgical delay, graft type, graft diameter, meniscal repair, remnant preservation, or excessive anterior graft tissue were not found to be associated with reoperation for cyclops syndrome.
Cong et al. (2025) studied this question.